Method for manufacturing solid electrolyte condensers

ABSTRACT

A method for manufacturing a solid electrolyte condenser encapsulated with an insulating resin, wherein a solder layer is partially formed on a cathode current collecting layer to be connected with a cathode terminal and the solder layer is subsequently remelted and solidified while contacted by the cathode terminal 5 to connect the cathode terminal 5 for the purpose of avoiding any possible spattering of solder of the solder layer connecting the cathode terminal to the cathode current collecting layer, any breakage or any defect in appearance.

FIELD OF TECHNOLOGY

This invention relates to a method for manufacturing a solid electrolytecondenser encapsulated with an insulating resin.

BACKGROUND ART

Hitherto, this type of solid electrolyte condenser was formed bypreparing a condenser element formed by sequentially depositing a layerof semiconductor metal oxide such as manganese dioxide, a cathode layermade of carbon and a cathode current collecting layer made of silverpaint, on an anode of a sintered body of valve metal such as tantalumhaving an anode lead-out line, which is made of a valve metal such astantalum, and also, having a surface thereof formed with a dielectricoxidizing film, and then encapsulating this condenser element with aninsulating resin. From this condenser body extend an anode terminalconnected to the anode lead-out line, and a cathode terminal connectedto the cathode current collecting layer.

In general, a chip component such as the solid electrolyte condenser issoldered to a land on a circuit board by passing, after it has beendirectly placed on the circuit board, through a furnace heated to 200°to 270° C. or fixed on the circuit board by the use of a bonding agentand soldered to the land on the circuit board by dipping the whole ofthe chip component in a solder bath with the chip component orienteddownwards, and for this reason the chip component tends to be heated to200° to 270° C. and, therefore, must have an appropriate heatresistance.

On the other hand, in the solid electrolyte condenser, soldering is usedin connecting the condenser element with the cathode terminal because ofits high workability and inexpensiveness, but in view of the fact thatthe silver paint is used to form the cathode current collecting layertends to erode more and more as the temperature increases, any solderhaving a melting point higher than 270° C. cannot be used and,therefore, a solder of about 183° to 270° C. is used.

In addition, in this type of solid electrolyte condenser, referring toFIG. 1(a), the cathode terminal is connected by dipping a condenserelement 1 with the conventional cathode current collecting layer formedthereon into a flux or rosin-isopropyl alcohol type to apply a flux 2thereto (Even though the condenser element is partially dipped into theflux, the flux adheres to the whole of the cathode current collectinglayer by capillary action), then dipping it into a solder bath of about200° to 230° C. to form a solder layer 3 on the cathode currentcollecting layer as shown in FIG. 1 (b), and finally dipping it againinto the solder bath while the cathode terminal is connected to thesolder layer 3.

However, where this type of solder is used, in view of the facts thatthe temperature at which soldering to the circuit board is performed isas high as 200° to 270° C. and that the whole is dipped into the solderbath, the solder inside tends to fuse and thermally expand enough tobreak a weak area of an encapsulating resin or to spatter outwards,resulting in breakage, resin cracking, a defect in appearance and otherdefects.

SUMMARY OF THE INVENTION

Accordingly, this invention is intended to provide a method formanufacturing a solid electrolyte condenser wherein the cathode terminalis connected by forming a solder layer partially on the cathode currentcollecting layer to be connected with the cathode terminal and thenremelting and solidifying the solder layer while said cathode terminalis held in contact with the solder layer, which method is free from anypossible spattering of solder and is effective to produce the condenserfree from any breakage or defect in appearance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) and (b) are perspective views showing part of theconventional method for manufacturing a solid electrolyte condenser;

FIGS. 2, 3, 4 and 5 are perspective views showing steps of a method formanufacturing a chip-like solid electrolyte condenser according to oneembodiment of this invention;

FIGS. 6(a) to 6(d) are diagrams showing essential steps of themanufacturing method of this invention;

FIG. 7 is a sectional view showing a dip-type solid electrolytecondenser according to another embodiment of this invention; and

FIG. 8 is a perspective view showing a condenser element of the samecondenser.

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 2 to 5 illustrate a method for manufacturing a chip-like solidelectrolyte condenser according to one embodiment of this invention and,in this embodiment, lead frames are employed wherein a plurality ofanode terminal pieces 4', which form an anode terminal, and a pluralityof cathode terminal pieces 5' which form a cathode terminal are soarranged as to have their tips held in abutment in predetermined spacedrelation.

In the first place, as shown in FIG. 2, a condenser element 6 isdisposed between the respective tips of the anode terminal pieces 4' andthe cathode terminal pieces 5' which are held in abutment. At this time,the anode and cathode terminal pieces 4' and 5' should be positionedabove the condenser element 6 with a U-shaped connecting area 5a' of thecathode terminal piece 5' engaged over the condenser element 6.

Subsequently, as shown in FIG. 3, an anode lead-out line 6a of thecondenser element 6 and a connecting area 4a' of the anode terminalpiece 4' are welded together and, also, the connecting area 5a' of thecathode terminal piece 5' is connected to a cathode current collectinglayer 6b on the condenser element 6 by means of a solder layer 6c formedon a portion of the cathode current collecting layer 6b.

At the time the connecting area 5a' of the cathode terminal piece 5' isto be connected to the cathode current collecting layer 6b by means ofthe solder layer 6c, the cathode terminal piece 5' is heated and, inaddition, the connecting 5a' is pressed towards the condenser element 6.This pressing is preferred to be continued until the solder solidifies.

Subsequently, by encapsulating to cause the condenser element 6including portions of the anode and cathode terminal pieces 4' and 5' tobe molded with an insulating resin 7 as shown by the broken line in FIG.4, then cutting the anode and cathode terminal pieces 4' and 5' atpredetermined positions and finally bending them along an end face and abottom surface of the condenser body 8 to provide the anode and cathodeterminals 4 and 5, the chip-like solid electrolyte condenser shown inFIG. 5 can be obtained. It is to be noted that reference numerals 4a'and 5a' designate the connecting areas.

Hereinafter, a method for forming the solder layer 6c partially on thecathode current collecting layer 6b on the condenser element 6 will bedescribed.

To begin with a first method, although a solderable silver paint, forexample, #4929 (commercial name) of Du'Pont of U.S.A., has long beenused as the cathode current collecting layer of the solid electrolytecondenser, these silver paints can be solderable, but any solder failsto attach to a silver paint layer when dipped into a solder bath withoutusing a flux. That is, soldering by to a dipping method, even thoughsolderable silver paint is used, is not effective.

Thus, by applying a flux only to a portion where soldering and asoldered coat are required, it is possible to form the solder layer onlyon that portion.

Since a solvent for the flux is an organic solvent such as xylene, bulylacetate or methyl Cellosolve, it exhibits a good permeability and, also,a good affinity for the silver paint and, therefore, even though aportion is dipped into a flux solution, the flux adheres to the totalsurface.

In view of the above, where the flux is to be applied, the flux ofisopropyl alcohol type is first caused to impregnate a porous materialsuch as glass fibers, brushes, sponge or cotton and, then, the porousmaterial is caused to contact to a portion of the silver paint layer onthe condenser element. By so doing, flux can accurately be applied andlimited to where soldering is required.

Steps of this method are shown in FIGS. 6(a) to 6(d) and, in thesefigures, reference numeral 9 designates a silver paint layer, referencenumeral 10 designates a flux, reference numeral 11 designates a solderbath, and reference numeral 12 designates a solder layer.

A second method will now be described. This second method is a methodwherein the cathode current collecting layer is constituted by anon-solderable silver paint and the solderable silver paint, thesolderable silver paint being applied to a portion which forms thesolder layer, and that portion is dipped into a solder bath after havingbeen applied with the flux over the entire surface of the cathodecurrent collecting layer. That is, according to this method, the solderlayer can be formed only on the solderable silver paint. The solderablesilver paint utilizeable in this method includes, for example #4922(commercial name) and #4929 (commercial name) of Du'Pont of U.S.A.whereas the non-solderable silver paint includes, for example, #5504(commercial name) and #6838 (commercial name) of Du'Pont of U.S.A.

With these two methods, it is possible to provide the solder layer onlyon the necessary portion.

Although in the foregoing description, silver paint has been describedas used for the cathode current collecting layer, other than silverpaint need be used. Moreover, even the flux may not be limited to thatin the above described embodiment.

The following table illustrates the results of tests in which thechip-like solid electrolyte condensers made by the manufacturing methodof this invention and the conventional chip-like solid electrolytecondensers were examined as to breakage and resin cracking resultingfrom the solder spattering by dipping the condensers into a solder bath,heated to 240° C., 260° C. and 280° C., for 5 seconds, 10 seconds, and20 seconds. Each numerical value in the table represents the number ofdefective condensers/the number of test-pieces.

    ______________________________________                                                Dipping Time                                                                           240° C.                                                                          260° C.                                                                        280° C.                             ______________________________________                                        Conventional                                                                             5 secs.   10/50     13/50 35/50                                    Invention             0/49      1/50  6/50                                    Conventional                                                                            10 secs.   15/49     21/50 41/50                                    Invention             0/50      3/50  7/50                                    Conventional                                                                            20 secs.   20/50     23/50 42/50                                    Invention             0/50      2/50  6/50                                    ______________________________________                                    

As stated above, with the manufacturing method of this invention, achip-like solid electrolyte condenser having an excellent heatresistance and free from any possible spattering of the solder used inconnection with the cathode terminal, which would occur when dipped intothe solder bath of 250° C., and from any breakage or defect inappearance can be obtained.

In addition, in the manufacturing method of this invention, by heatingthe cathode terminal while pressed towards the condenser element at thetime the cathode terminal is to be connected to the cathode currentcollecting layer, it is possible to connect the cathode terminal with nofault and, also, with no formation of any unnecessary space between thecathode terminal and the condenser element, and an advantage can beappreciated in the minimization in size.

In addition, although the foregoing description has been made inconnection with the chip-like solid electrolyte condenser, it mayequally apply to other types of solid electrolyte condensers.Specifically, even in a solid electrolyte condenser encapsulated bydipping or encapsulated by molding and wherein a lead line is used aseach of the anode and cathode terminals, the recent trend is that thesoldering condition becomes strict and the occasion is increasingwherein the body of a condenser is, after the lead lines have beeninserted through perforations in a printed circuit board, forced todirectly contact the printed circuit board. Because of this, the demandhas increased to make this type of solid electrolyte condenser have aheat resistance comparable to that of the chip-like solid electrolytecondenser.

An embodiment in which this invention is applied to this type of solidelectrolyte condenser is shown in FIGS. 7 and 8 wherein referencenumeral 13 designates an anode lead line and reference numeral 14designate a cathode lead line. In this embodiment, the solder layer 6cis partially formed on the cathode current collecting layer 6b on thecondenser element 6 which is to be connected with the cathode lead line14, and the cathode lead line 14 is connected by remelting andsolidifying the solder layer 6c while the cathode lead 14 is in contactwith the solder layer 6c.

INDUSTRIAL APPLICABILITY

As hereinbefore described, since the method for manufacturing the solidelectrolyte condenser according to this invention is such that thesolder layer is partially formed on the cathode current collecting layerto be connected with the cathode terminal and the cathode terminal isthen connected by remelting and solidifying the solder layer whilecontacting the solder layer, there is neither any possible breakage of aweak area of the encapsulating resin nor any possible spattering of thesolder from the surface of the boundary between the cathode terminal andthe encapsulating resin, even when the solder layer connecting thecathode terminal and the cathode current collecting layer undergoes athermal expansion and, therefore, the solid electrolyte condenser havingan excellent heat resistance and free from any breakage, resin crackingor defect in appearance even when dipped into the solder bath of hightemperature during the soldering to the circuit board, can be obtained.

I claim:
 1. A method of manufacturing a solid electrolyte condenser,comprising the steps of:a. providing a condenser element which includesa layer of semiconductor metal, a cathode layer and a cathode currentcollecting layer sequentially deposited on an anode body having an anodelead-out line and a surface having a dielectric oxide film thereon; b.forming a solder layer on a portion less than the whole of said cathodecurrent collecting layer by applying a flux to said portion andsubsequently dipping the condenser element into a solder bath; c.remelting and subsequently solidifying the solder layer while contactingthe solder layer with a cathode terminal so as to connect the cathodeterminal to the cathode current collecting layer; d. connecting an anodeterminal to the anode lead-out line; and e. encapsulating the condenserelement after the anode and cathode terminals are respectively connectedto the anode lead-out line and the cathode current collecting layer. 2.A method as defined in claim 1, wherein the step of remelting andsolidifying includes the step of melting the solder layer by heating theside of the cathode terminal and applying the heated cathode terminal tothe solder layer.
 3. A method as defined in claim 1, wherein the flux isapplied by contacting a porous material impregnated with the flux to theportion where the solder layer is to be formed.
 4. A method as definedin claim 2, wherein the step of remelting and solidifying includes thestep of pressing the cathode layer against the condenser element duringthe heating.
 5. A method of manufacturing a solid electrolyte condenser,comprising the steps of:a. providing a condenser element which includesthree layers, including(1) a layer of semiconductor metal, (2) a cathodelayer, and (3) a cathode current collecting layer formed of a solderableelectroconductive portion and a non-solderable electroconductiveportion, sequentially deposited on an anode body having an anodelead-out line and a surface having a dielectric oxide film thereon; b.forming a solder layer on a portion less than the whole of said cathodecurrent collecting layer by applying a flux to the whole of said cathodecurrent collecting layer and subsequently dipping the condenser elementinto a solder bath to form the solder layer on the solderable portion ofthe cathode current collecting layer; c. remelting and subsequentlysolidifying the solder layer while contacting the solder layer with acathode terminal so as to connect the cathode terminal to the cathodecurrent collecting layer; d. connecting an anode terminal to the anodelead-out line; and e. encapsulating the condenser element after theanode and cathode terminals are respectively connected to the anodelead-out line and the cathode current collecting layer.
 6. A method asdefined in claim 5, wherein the step of remelting and solidifyingincludes the step of melting the solder layer by heating the side of thecathode terminal and applying the heated cathode terminal to the solderlayer.
 7. A method as defined in claim 6, wherein the step of remeltingand solidifying includes the step of pressing the cathode layer againstthe condenser element during the heating.